Three-dimensional dendrite-tip morphology

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Abstract
We investigated the morphology of dendrite tips through the growth and measurement of pure succinonitrile dendrites at a fixed supercooling of 0.46 K. Many current theories of dendritic growth rely on the assumption that the tip region can be approximated by a paraboloid of revolution. The evidence presented here suggests that this assumption becomes invalid in regions only slightly removed from the tip and well before the appearance of side branches. Characterization of dendrites using a fourth-order polynomial, with fourfold rotational symmetry, provides a useful description of the dendrite extending to regions up to eight radii from the tip. This has also enabled a more precise determination of the shape and size of a dendrite tip than was heretofore possible. This includes information about the anisotropy of the interface morphology.